Televisions, mobile phones, tablets, digital cameras, MP3 players, and other portable and non-portable electronic devices utilize light-emitting diodes (“LEDs”), organic light-emitting diodes (“OLEDs”), polymer light-emitting diodes (“PLEDs”), and other solid-state transducer (“SST”) devices for, e.g., backlighting. SST devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination. FIG. 1A is a cross-sectional view of a conventional SST device 10a with lateral contacts. As shown in FIG. 1A, the SST device 10a includes a substrate 20 carrying an LED structure 11 having an active region 14, e.g., containing gallium nitride/indium gallium nitride (GaN/InGaN) multiple quantum wells (“MQWs”) between N-type GaN 15 and P-type GaN 16. The SST device 10a also includes a first contact 17 on a forward-facing surface of the P-type GaN 16 and a second contact 19 spaced laterally apart from the first contact 17 on a forward-facing surface of the N-type GaN 15. The first contact 17 typically includes a transparent and conductive material (e.g., indium tin oxide (“ITO”)) through which light is emitted from the LED structure 11. FIG. 1B is a cross-sectional view of another conventional SST device 10b in which the first and second contacts 17 and 19 are at opposite sides of the LED structure 11 in a vertical configuration rather than a lateral configuration. In the SST device 10b, the first contact 17 typically includes a reflective and conductive material (e.g., aluminum) to direct light toward the N-type GaN 15.
One difficulty of forming SST devices is that manufacturing the various semiconductor materials occurs at elevated temperatures. For example, GaN materials (e.g., the N-type GaN 15 or the P-type GaN 16) can be formed by epitaxial growth processes that use elevated temperatures to facilitate growth. In many instances, the elevated temperatures are difficult to control and can lead to uneven film growth and material defects.